Digital fluid level transducer/senders that are both rugged and lightweight could be used in fuel tanks for unmanned aircraft. Transducers capable of sustaining loads induced by launch, flight and landing are currently of an analog design, which imparts additional equipment needs on the system.
Digital transducers currently on the market are long, fragile instruments best suited for the lab or static tank environment with large spaces available for the bulky converters/senders mounted to the end of the instrument and external to the tank.
Linear variable differential transformers (LVDT), available with digital outputs, initially existed only in laboratories for positional measurement; however their robustness and capacity for surviving shock loads allowed their use in the field.
LVDTs, unfortunately, have been designed around a static LVDT transducer with a translating core. This design results in a product whose overall extended length is at least twice that which is to be measured. The volume to accommodate this length is not a luxury available within the unmanned aircraft structure.
Therefore, a digital level sensing apparatus is needed that can meet the size and weight constraints of an unmanned aircraft that is rugged enough to withstand this challenging environment.